Dual Specificity Antibody Fusions

ABSTRACT

The present invention provides dual specificity antibody fusion proteins comprising an antibody Fab or Fab′ fragment with specificity for an antigen of interest, said fragment being fused to at least one single domain antibody which has specificity for a second antigen of interest.

The present invention relates to new dual specificity antibody fusionproteins. Such antibodies comprise a first specificity to an antigen ofinterest, and a second specificity for a second antigen of interest, forexample a serum carrier protein for use in extending their in vivo serumhalf-life. Methods for the production of such molecules andpharmaceutical compositions comprising them are also provided.

The high specificity and affinity of antibodies makes them idealdiagnostic and therapeutic agents, particularly for modulatingprotein:protein interactions. Advances in the field of recombinantantibody technology have resulted in the production of antibodyfragments, such as Fv, Fab, Fab′ and F(ab′)₂ fragments and otherantibody fragments. These smaller molecules retain the antigen bindingactivity of whole antibodies and can also exhibit improved tissuepenetration and pharmacokinetic properties in comparison to wholeimmunoglobulin molecules. Indeed, antibody fragments are proving to beversatile therapeutic agents, as seen by the recent success of productssuch as ReoPro® and Lucentis®. Whilst such fragments appear to exhibit anumber of advantages over whole immunoglobulins, they also suffer froman increased rate of clearance from serum since they lack the Fc domainthat imparts a long lifetime in vivo (Medasan et al., 1997, J. Immunol.158:2211-2217).

Antibodies with dual specificity, i.e. which bind to two differentantigens have been previously described (for reviews, see Segal et al.,1999, Curr. Opin. Immunol. 11:558-562; Plückthun & Pack, 1997,Immunotechnology, 3:83-105; Fischer and Leger, 2007, Pathobiology, 74,3-14). Dual specificity antibodies are also described in WO02/02773,US2007065440, US2006257406, US2006106203 and US2006280734. Previousapproaches to making hetero-bispecific antibody-based molecules havegenerally employed chemical cross-linking or protein engineeringtechniques. Chemical cross-linking suffers from poor yields of hetero-and homo-dimer formation and the requirement for their subsequentchromatographic separation. Protein engineering approaches have eitherbeen highly elaborate (e.g. knobs-into-holes engineering; Ridgway etal., 1996, Protein Eng. 9(7):617-621) or have used molecules withinappropriate stability characteristics (e.g. diabodies, scFv). In somecases bispecific antibodies can also suffer from steric hindranceproblems such that both antigens cannot bind simultaneously to eachantibody arm.

Single variable domain antibodies also known as single domain antibodiesor dAbs, correspond to the variable regions of either the heavy (VH) orlight (VL) chain of an antibody. Murine single-domain antibodies weredescribed by Ward et al., 1989, Nature, 341, 544-546. Human and‘camelised’ human single domain antibodies have also been described(Holt et al., 2003, Trends in Biotechnology, 21, 484-490). Single domainantibodies have also been obtained from the camelids (camels and llamas)and cartilaginous fish (wobbegong and nurse sharks). These organismshave evolved high affinity single V-like domains (called VhH in camelidsand V-NAR in sharks), mounted on an Fc-equivalent constant domainframework as an integral and crucial component of their immune system(see Holliger & Hudson, for a review; 2005, Nature Biotechnology,23(9):1126-1136).

Single domain antibody-enzyme fusions have been described in EP0368684.Single domain-effector group fusions have also been described inWO2004/058820 which comprise a single variable domain. Dual variabledomain immunoglobulins have been described in WO2007/024715. Dualspecific ligands comprising two single domain antibodies with differingspecificities have been described in EP 1517921.

Means to improve the half-life of antibody fragments, such as Fv, Fab,Fab′, F(ab′)₂ and other antibody fragments, are known. One approach hasbeen to conjugate the fragment to polymer molecules. Thus, the shortcirculating half-life of Fab′, F(ab′)₂ fragments in animals has beenimproved by conjugation to polyethylene glycol (PEG; see, for example,WO98/25791, WO99/64460 and WO98/37200). Another approach has been tomodify the antibody fragment by conjugation to an agent that interactswith the FcRn receptor (see, for example, WO97/34631). Yet anotherapproach to extend half-life has been to use polypeptides that bindserum albumin (see, for example, Smith et al., 2001, Bioconjugate Chem.12:750-756; EP0486525; U.S. Pat. No. 6,267,964; WO04/001064;WO02/076489; and WO01/45746). However, there still remains a need toproduce antigen-binding immunoglobulin proteins that have a long in vivohalf-life, as an alternative to those that have a long half life becausethey interact with the FcRn receptor, without being chemically modifiedby conjugation to PEG, or being conjugated to human serum albumin.

A variety of proteins exist in plasma and include thyroxine-bindingprotein, transthyretin, α1-acid glycoprotein, transferrin, fibrinogenand albumin, or a fragment of any thereof Serum carrier proteinscirculate within the body with half-lives measured in days, for example,5 days for thyroxine-binding protein or 2 days for transthyretin(Bartalena & Robbins, 1993, Clinics in Lab. Med. 13:583-598), or 65hours in the second phase of turnover of iodinated α1-acid glycoprotein(Bree et al., 1986, Clin. Pharmacokin. 11:336-342). Data from Gitlin etal. (1964, J. Clin. Invest. 10:1938-1951) suggest that in pregnantwomen, the half-life of α1-acid glycoprotein is 3.8 days, 12 days fortransferrin and 2.5 days for fibrinogen. Serum albumin is an abundantprotein in both vascular and extravascular compartments with a half-lifein man of about 19 days (Peters, 1985, Adv Protein Chem. 37:161-245).This is similar to the half-life of IgG1, which is about 21 days(Waldeman & Strober, 1969, Progr. Allergy, 13:1-110).

The present invention provides improved dual specificity antibody fusionproteins which can be produced recombinantly and are capable of bindingtwo antigens simultaneously.

Thus, the present invention provides dual specificity antibody fusionproteins which comprise an immunoglobulin moiety with a firstspecificity for an antigen of interest, and further comprise a singledomain antibody (dAb) with specificity for a second antigen of interest.

The present invention also provides dual specificity antibody fusionproteins which comprise an immunoglobulin moiety with a firstspecificity for an antigen of interest, and further comprise at leastone single domain antibody with specificity for a second antigen ofinterest.

A dual specificity antibody fusion of the invention will be capable ofselectively binding to two antigens of interest.

In one embodiment, an antigen of interest bound by the Fab or Fab′fragment may be a cell-associated protein, for example a cell surfaceprotein on cells such as bacterial cells, yeast cells, T-cells,endothelial cells or tumour cells, or it may be a soluble protein.Antigens of interest may also be any medically relevant protein such asthose proteins upregulated during disease or infection, for examplereceptors and/or their corresponding ligands. Particular examples ofcell surface proteins include adhesion molecules, for example integrinssuch as β1 integrins e.g. VLA-4, E-selectin, P selectin or L-selectin,CD2, CD3, CD4, CD5, CD7, CD8, CD11a, CD11b, CD18, CD19, CD20, CD23,CD25, CD33, CD38, CD40, CD45, CDW52, CD69, CD134 (OX40), ICOS, BCMP7,CD137, CD27L, CDCP1, DPCR1, DPCR1, dudulin2, FLJ20584, FLJ40787, HEK2,KIAA0634, KIAA0659, KIAA1246, KIAA1455, LTBP2, LTK, MAL2, MRP2,nectin-like2, NKCC1, PTK7, RAIG1, TCAM1, SC6, BCMP101, BCMP84, BCMP11,DTD, carcinoembryonic antigen (CEA), human milk fat globulin (HMFG1 and2), MHC Class I and MHC Class II antigens, and VEGF, and whereappropriate, receptors thereof.

Soluble antigens include interleukins such as IL-1, IL-2, IL-3, IL-4,IL-5, IL-6, IL-8, IL-12, IL-16 or IL-17, viral antigens for examplerespiratory syncytial virus or cytomegalovirus antigens,immunoglobulins, such as IgE, interferons such as interferon α,interferon β or interferon γ, tumour necrosis factor-α, tumor necrosisfactor-β, colony stimulating factors such as G-CSF or GM-CSF, andplatelet derived growth factors such as PDGF-α, and PDGF-β and whereappropriate receptors thereof Other antigens include bacterial cellsurface antigens, bacterial toxins, viruses such as influenza, EBV,HepA, B and C, bioterrorism agents, radionuclides and heavy metals, andsnake and spider venoms and toxins.

In one embodiment, the antibody fusion protein of the invention may beused to functionally alter the activity of the antigen of interest. Forexample, the antibody fusion protein may neutralize, antagonize oragonise the activity of said antigen, directly or indirectly.

In one embodiment, a second antigen of interest bound by the singledomain antibody or antibodies in the dual specificity antibody fusionproteins of the invention may be a cell-associated protein, for examplea cell surface protein on cells such as bacterial cells, yeast cells,T-cells, endothelial cells or tumour cells, or it may be a solubleprotein. Antigens of interest may also be any medically relevant proteinsuch as those proteins upregulated during disease or infection, forexample receptors and/or their corresponding ligands. Particularexamples of cell surface proteins include adhesion molecules, forexample integrins such as β1 integrins e.g. VLA-4, E-selectin, Pselectin or L-selectin, CD2, CD3, CD4, CD5, CD7, CD8, CD11a, CD11b,CD18, CD19, CD20, CD23, CD25, CD33, CD38, CD40, CD45, CDW52, CD69, CD134(OX40), ICOS, BCMP7, CD137, CD27L, CDCP1, DPCR1, DPCR1, dudulin2,FLJ20584, FLJ40787, HEK2, KIAA0634, KIAA0659, KIAA1246, KIAA1455, LTBP2,LTK, MAL2, MRP2, nectin-like2, NKCC1, PTK7, RAIG1, TCAM1, SC6, BCMP101,BCMP84, BCMP11, DTD, carcinoembryonic antigen (CEA), human milk fatglobulin (HMFG1 and 2), MHC Class I and MHC Class II antigens, and VEGF,and where appropriate, receptors thereof.

Soluble antigens include interleukins such as IL-1, IL-2, IL-3, IL-4,IL-5, IL-6, IL-8, IL-12, IL-16 or IL-17, viral antigens for examplerespiratory syncytial virus or cytomegalovirus antigens,immunoglobulins, such as IgE, interferons such as interferon α,interferon β or interferon γ, tumour necrosis factor-α, tumor necrosisfactor-β, colony stimulating factors such as G-CSF or GM-CSF, andplatelet derived growth factors such as PDGF-α, and PDGF-β and whereappropriate receptors thereof. Other antigens include bacterial cellsurface antigens, bacterial toxins, viruses such as influenza, EBV,HepA, B and C, bioterrorism agents, radionuclides and heavy metals, andsnake and spider venoms and toxins.

Other antigens which may be bound by the single domain antibody orantibodies include serum carrier proteins, polypeptides which enablecell-mediated effector function recruitment and nuclide chelatorproteins.

Thus, in one example the present invention provides dual specificityantibody fusion proteins which comprise an immunoglobulin moiety with afirst specificity for an antigen of interest, and further comprise asingle domain antibody with specificity for a second protein, the latterproviding the ability to recruit effector functions, such as complementpathway activation and/or effector cell recruitment. Further, fusionproteins of the present invention may be used to chelate radionuclidesby virtue of a single domain antibody which binds to a nuclide chelatorprotein. Such fusion proteins are of use in imaging or radionuclidetargeting approaches to therapy.

Accordingly, in one example there is provided an isolated dualspecificity antibody fusion protein comprising an antibody Fab or Fab′fragment with specificity for an antigen of interest, said fragmentbeing fused to at least one dAb which has specificity for a recruitmentpolypeptide, said dAb providing the ability to recruit cell-mediatedeffector function(s), directly or indirectly, by binding to saidrecruitment polypeptide.

The recruitment of effector function may be direct in that effectorfunction is associated with a cell, said cell bearing a recruitmentmolecule on its surface. Indirect recruitment may occur when binding ofa dAb to a recruitment molecule causes release of, for example, a factorwhich in turn may directly or indirectly recruit effector function, ormay be via activation of a signalling pathway. Examples include TNFα,IL2, IL6, IL8, IL17, IFNγ, histamine, Clq, opsonin and other members ofthe classical and alternative complement activation cascades, such asC2, C4, C3-convertase, and C5 to C9.

As used herein, ‘a recruitment polypeptide’ includes a FcγR such asFcγRI, FcγRII and FcγRIII, a complement pathway protein such as, butwithout limitation, Clq and C3, a CD marker protein (Cluster ofDifferentiation marker) such as, but without limitation, CD68, CD115,CD16, CD80, CD83, CD86, CD56, CD64, CD3, CD4, CD8, CD28, CD45, CD19,CD20 and CD22. Further recruitment polypeptides which are CD markerproteins include CD1, CD1d, CD2, CDS, CD8, CD9, CD10, CD11, CD11a,CD11b, CD11c, CD13, CD14, CD15, CD16, CD18, CD19, CD20, CD21, CD22,CD23, CD24, CD25, CD26, CD27, CD28, CD29, CD30, CD31, CD32, CD33, CD34,CD35, CD36, CD37, CD38, CD40, CD43, CD44, CD45, CD46, CD49, CD49a,CD49b, CD49c, CD49d, CD52, CD53, CD54, CD55, CD56, CD58, CD59, CD61,CD62, D62E, CD62L, CD62P, CD63, CD64, CD66e, CD68, CD70, CD71, CD72,CD79, CD80, CD81, CD82, CD83, CD84, CD85, CD86, CD88, CD89, CD90, CD94,CD95, CD98, CD106, CD114, CD116, CD117, CD118, CD120, CD122, CD130,CD131, CD132, CD133, CD134, CD135, CD137, CD138, CD141, CD142, CD143,CD146, CD147, CD151, CD152, CD153, CD154, CD155, CD162, CD164, CD169,CD184, CD206, CD209, CD257, CD278, CD281, CD282, CD283 and CD304, or afragment of any thereof which retains the ability to recruitcell-mediated effector function either directly or indirectly. Arecruitment polypeptide also includes immunoglobulin molecules such asIgG1, IgG2, IgG3, IgG4, IgE and IgA which possess effector function.

In one embodiment, the second protein for which the dAb has specificityis a complement pathway protein, with Clq being particularly preferred.

In a preferred embodiment, the second protein for which the dAb hasspecificity is a CD marker protein, with CD68, CD80, CD86, CD64, CD3,CD4, CD8 CD45, CD16 and CD35 being particularly preferred.

Accordingly also provided is an isolated dual specificity antibodyfusion protein comprising an antibody fragment with specificity for anantigen of interest, said fragment being fused to at least one dAb whichhas specificity for a CD molecule selected from the group consisting ofCD68, CD80, CD86, CD64, CD3, CD4, CD8 CD45, CD16 and CD35.

In one embodiment the single domain antibody or antibodies provide anextended half-life to the immunoglobulin moiety with the firstspecificity.

Accordingly, in one embodiment there is provided a dual specificityantibody fusion protein comprising an antibody Fab or Fab′ fragment withspecificity for an antigen of interest, said fragment being fused to atleast one single domain antibody which has specificity for a serumcarrier protein, a circulating immunoglobulin molecule, or CD35/CR1,said single domain antibody providing an extended half-life to theantibody fragment with specificity for said antigen of interest bybinding to said serum carrier protein, circulating immunoglobulinmolecule or CD35/CR1.

In one embodiment there is provided an isolated dual specificityantibody fusion protein comprising an antibody Fab or Fab′ fragment withspecificity for an antigen of interest, said fragment being fused to atleast one single domain antibody which has specificity for a serumcarrier protein, a circulating immunoglobulin molecule, or CD35/CR1,said single domain antibody providing an extended half-life to theantibody fragment with specificity for said antigen of interest bybinding to said serum carrier protein, circulating immunoglobulinmolecule or CD35/CR1.

As used herein, ‘serum carrier proteins’ include thyroxine-bindingprotein, transthyretin, α1-acid glycoprotein, transferrin, fibrinogenand albumin, or a fragment of any thereof.

As used herein, a ‘circulating immunoglobulin molecule’ includes IgG1,IgG2, IgG3, IgG4, sIgA, IgM and IgD, or a fragment of any thereof

CD35/CR1 is a protein present on red blood cells which have a half lifeof 36 days (normal range of 28 to 47 days; Lanaro et al., 1971, Cancer,28(3):658-661).

In a preferred embodiment, the second protein for which the dAb hasspecificity is a serum carrier protein, with a human serum carrierprotein being particularly preferred. In a most preferred embodiment,the serum carrier protein is human serum albumin.

Accordingly provided is a dual specificity antibody fusion proteincomprising an antibody Fab or Fab′ fragment with specificity for anantigen of interest, said fragment being fused to at least one singledomain antibody which has specificity for human serum albumin.

In one embodiment the present invention provides an isolated dualspecificity antibody fusion protein comprising an antibody Fab or Fab′fragment with specificity for an antigen of interest, said fragmentbeing fused to at least one single domain antibody which has specificityfor human serum albumin.

In one embodiment, the antibody fragment with specificity for an antigenof interest is a Fab fragment. In another embodiment, the antibodyfragment with specificity for an antigen of interest is a Fab′ fragment.

Thus, in one most preferred embodiment, the antibody fusion proteins ofthe invention are translation fusion proteins, i.e. genetic fusions, thesequence of each of which is encoded by an expression vector.Alternatively, the antibody fusion protein components have been fusedusing chemical means, i.e. by chemical conjugation or chemicalcross-linking. Such chemical means are known in the art.

In one example, the antibody fragments are Fab′ fragments which possessa native or a modified hinge region. Where the antibody fragment for usein preparing a dual specificity antibody fusion protein of the inventionis a Fab′ fragment, said fragment is generally extended at theC-terminus of the heavy chain by one or more amino acids. Thus, anantibody fusion of the invention can comprise a Fab′ fragmenttranslation fused (or chemically fused) to a dAb, directly or via alinker. Further, examples of suitable antibody Fab′ fragments includethose described in WO2005003170 and WO2005003171.

In another example, the antibody fragments are Fab fragments. Thus, anantibody fusion of the invention can comprise a Fab fragment translationfused (or chemically fused) to a linker sequence which in turn istranslation fused (or chemically fused) to a dAb. Preferably, the Fabfragment is a Fab fragment which terminates at the interchain cysteines,as described in WO2005/003169.

The antibody Fab or Fab′ fragments of use in the present invention canbe from any species but are preferably derived from a monoclonalantibody, a human antibody, or are humanised fragments. An antibodyfragment for use in the present invention can be derived from any class(e.g. IgG, IgE, IgM, IgD or IgA) or subclass of immunoglobulin moleculeand may be obtained from any species including for example mouse, rat,shark, rabbit, pig, hamster, camel, llama, goat or human.

In one embodiment, the antibody Fab or Fab′ fragment is a monoclonal,fully human, humanized or chimeric antibody fragment. In one embodimentthe antibody Fab or Fab′ fragments are fully human or humanised.

Monoclonal antibodies may be prepared by any method known in the artsuch as the hybridoma technique (Kohler & Milstein, Nature, 1975, 256,495-497), the trioma technique, the human B-cell hybridoma technique(Kozbor et al., Immunology Today, 1983, 4, 72) and the EBV-hybridomatechnique (Cole et al., “Monoclonal Antibodies and Cancer Therapy”, pp.77-96, Alan R. Liss, Inc., 1985).

Antibodies for use in the invention may also be generated using singlelymphocyte antibody methods by cloning and expressing immunoglobulinvariable region cDNAs generated from single lymphocytes selected for theproduction of specific antibodies by, for example, the methods describedby Babcook, J. et al., Proc. Natl. Acad. Sci. USA, 1996, 93(15),7843-7848, WO 92/02551, WO2004/051268 and WO2004/106377.

Humanized antibodies are antibody molecules from non-human specieshaving one or more complementarity determining regions (CDRs) from thenon-human species and a framework region from a human immunoglobulinmolecule (see, for example, U.S. Pat. No. 5,585,089).

The antibodies for use in the present invention can also be generatedusing various phage display methods known in the art and include thosedisclosed by Brinkman et al., J. Immunol. Methods, 1995, 182, 41-50;Ames et al., J. Immunol. Methods, 1995, 184, 177-186; Kettleborough etal. Eur. J. Immunol., 1994, 24, 952-958; Persic et al., Gene, 1997 187,9-18; and Burton et al., Advances in Immunology, 1994, 57, 191-280; WO90/02809; WO 91/10737; WO 92/01047; WO 92/18619; WO 93/11236; WO95/15982; and WO 95/20401; and U.S. Pat. Nos. 5,698,426; 5,223,409;5,403,484; 5,580,717; 5,427,908; 5,750,753; 5,821,047; 5,571,698;5,427,908; 5,516,637; 5,780,225; 5,658,727; 5,733,743; and 5,969,108.Also, transgenic mice, or other organisms, including other mammals, maybe used to generate humanized antibodies.

Fully human antibodies are those antibodies in which the variableregions and the constant regions (where present) of both the heavy andthe light chains are all of human origin, or substantially identical tosequences of human origin, not necessarily from the same antibody.Examples of fully human antibodies may include antibodies produced forexample by the phage display methods described above and antibodiesproduced by mice in which the murine immunoglobulin variable andconstant region genes have been replaced by their human counterparts eg.as described in general terms in EP0546073 B1, U.S. Pat. No. 5,545,806,U.S. Pat. No. 5,569,825, U.S. Pat. No. 5,625,126, U.S. Pat. No.5,633,425, U.S. Pat. No. 5,661,016, U.S. Pat. No. 5,770,429, EP 0438474B1 and EP0463151 B1.

The antibody Fab or Fab′ fragment starting material for use in thepresent invention may be obtained from any whole antibody, especially awhole monoclonal antibody, using any suitable enzymatic cleavage and/ordigestion techniques, for example by treatment with pepsin.Alternatively, or in addition the antibody starting material may beprepared by the use of recombinant DNA techniques involving themanipulation and re-expression of DNA encoding antibody variable and/orconstant regions. Standard molecular biology techniques may be used tomodify, add or delete amino acids or domains as desired. Any alterationsto the variable or constant regions are still encompassed by the terms‘variable’ and ‘constant’ regions as used herein.

The antibody fragment starting material may be obtained from any speciesincluding for example mouse, rat, rabbit, hamster, camel, llama, goat orhuman. Parts of the antibody fragment may be obtained from more than onespecies, for example the antibody fragments may be chimeric. In oneexample, the constant regions are from one species and the variableregions from another. The antibody fragment starting material may alsobe modified. In another example, the variable region of the antibodyfragment has been created using recombinant DNA engineering techniques.Such engineered versions include those created for example from naturalantibody variable regions by insertions, deletions or changes in or tothe amino acid sequences of the natural antibodies. Particular examplesof this type include those engineered variable region domains containingat least one CDR and, optionally, one or more framework amino acids fromone antibody and the remainder of the variable region domain from asecond antibody. The methods for creating and manufacturing theseantibody fragments are well known in the art (see for example, Boss etal., U.S. Pat. No. 4,816,397; Cabilly et al., U.S. Pat. No. 6,331,415;Shrader et al., WO 92/02551; Ward et al., 1989, Nature, 341, 544;Orlandi et al., 1989, Proc. Natl. Acad. Sci. USA, 86, 3833; Riechmann etal., 1988, Nature, 322, 323; Bird et al, 1988, Science, 242, 423; Queenet al., U.S. Pat. No. 5,585,089; Adair, WO91/09967; Mountain and Adair,1992, Biotechnol. Genet. Eng. Rev, 10, 1-142; Verma et al., 1998,Journal of Immunological Methods, 216, 165-181).

In the present invention each single domain antibody fused to the Fab orFab′ fragment may linked directly or via a linker.

Examples of suitable linker regions for linking a dAb to a Fab or Fab′include, but are not limited to, flexible linker sequences and rigidlinker sequences. Flexible linker sequences include those disclosed inHuston et al., 1988, PNAS 85:5879-5883; Wright & Deonarain, Mol.Immunol., 2007, 44(11):2860-2869; Alfthan et al., Prot. Eng., 1995,8(7):725-731; Luo et al., J. Biochem., 1995, 118(4):825-831; Tang etal., 1996, J. Biol. Chem. 271(26):15682-15686; and Turner et al., 1997,JIMM 205, 42-54 (see Table 1 for representative examples).

TABLE 1  Flexible linker sequences SEQ ID NO: SEQUENCE 1 SGGGGSE 2DKTHTS 3 GGGGS 45 GGGGSGGGGS 46 GGGGSGGGGSGGGGS 47 GGGGSGGGGSGGGGSGGGGS48 GGGGSGGGGSGGGGSGGGGSGGGGS 4 AAAGSG-GASAS 5 AAAGSG-XGGGS-GASAS 49AAAGSG-XGGGSXGGGS-GASAS 50 AAAGSG-XGGGSXGGGSXGGGS-GASAS 51AAAGSG-XGGGSXGGGSXGGGSXGGGS-GASAS 6 AAAGSG-XS-GASAS 7PGGNRGTTTTRRPATTTGSSPGPTQSHY 8 ATTTGSSPGPT 9 ATTTGS — GS 10EPSGPISTINSPPSKESHKSP 11 GTVAAPSVFIFPPSD 12 GGGGIAPSMVGGGGS 13GGGGKVEGAGGGGGS 14 GGGGSMKSHDGGGGS 15 GGGGNLITIVGGGGS 16 GGGGVVPSLPGGGGS17 GGEKSIPGGGGS 18 RPLSYRPPFPFGFPSVRP 19 YPRSIYIRRRHPSPSLTT 20TPSHLSHILPSFGLPTFN 21 RPVSPFTFPRLSNSWLPA 22 SPAAHFPRSIPRPGPIRT 23APGPSAPSHRSLPSRAFG 24 PRNSIHFLHPLLVAPLGA 25 MPSLSGVLQVRYLSPPDL 26SPQYPSPLTLTLPPHPSL 27 NPSLNPPSYLHRAPSRIS 28 LPWRTSLLPSLPLRRRP 29PPLFAKGPVGLLSRSFPP 30 VPPAPVVSLRSAHARPPY 31 LRPTPPRVRSYTCCPTP- 32PNVAHVLPLLTVPWDNLR 33 CNPLLPLCARSPAVRTFP

Examples of rigid linkers include the peptide sequences GAPAPAAPAPA (SEQID NO:34), PPPP (SEQ ID NO:35) and PPP.

In one embodiment, an antibody hinge sequence or part thereof is used asa linker, eg. the upper hinge sequence. Typically, antibody Fab′fragments for use in the present invention possess a native or amodified hinge region. Such hinge regions are used as a natural linkerto the dAb moiety. The native hinge region is the hinge region normallyassociated with the C_(H)1 domain of the antibody molecule. A modifiedhinge region is any hinge that differs in length and/or composition fromthe native hinge region. Such hinges can include hinge regions from anyother species, such as human, mouse, rat, rabbit, hamster, camel, llamaor goat hinge regions. Other modified hinge regions may comprise acomplete hinge region derived from an antibody of a different class orsubclass from that of the C_(H)1 domain. Thus, for instance, a C_(H)1domain of class yl may be attached to a hinge region of class γ4.Alternatively, the modified hinge region may comprise part of a naturalhinge or a repeating unit in which each unit in the repeat is derivedfrom a natural hinge region. In a further alternative, the natural hingeregion may be altered by converting one or more cysteine or otherresidues into neutral residues, such as alanine, or by convertingsuitably placed residues into cysteine residues. By such means thenumber of cysteine residues in the hinge region may be increased ordecreased. In addition other characteristics of the hinge can becontrolled, such as the distance of the hinge cysteine(s) from the lightchain interchain cysteine, the distance between the cysteines of thehinge and the composition of other amino acids in the hinge that mayaffect properties of the hinge such as flexibility e.g. glycines may beincorporated into the hinge to increase rotational flexibility orprolines may be incorporated to reduce flexibility. Alternativelycombinations of charged or hydrophobic residues may be incorporated intothe hinge to confer multimerisation properties, see for example, Richteret al., 2001, Prot. Eng. 14(10):775-783 for use of charged or ionictails, e.g., acidic tails as linkers and Kostelny et al., 1992, J.Immunol. 5(1):1547-1553 for leucine zipper sequences. Other modifiedhinge regions may be entirely synthetic and may be designed to possessdesired properties such as length, composition and flexibility.

A number of modified hinge regions have already been described forexample, in U.S. Pat. No. 5,677,425, U.S. Pat. No. 6,642,356, WO9915549,WO2005003170, WO2005003169, WO2005003170, WO9825971 and WO2005003171 andthese are incorporated herein by reference. Such hinges generally followon from the CH1 region, but may also be incorporated onto the end ofconstant region of a light chain kappa or lambda fragment; see Table 2for examples.

TABLE 2  Hinge linker sequences SEQ ID NO: SEQUENCE 36 DKTHTCAA 37DKTHTCPPCPA 38 DKTHTCPPCPATCPPCPA 39 DKTHTCPPCPATCPPCPATCPPCPA 40DKTHTCPPCPAGKPTLYNSLVMSDTAGTCY 41 DKTHTCPPCPAGKPTHVNVSVVMAEVDGTCY 42DKTHTCCVECPPCPA 43 DKTHTCPRCPEPKSCDTPPPCPRCPA 44 DKTHTCPSCPA

Single variable domains also known as single domain antibodies or dAbsfor use in the present invention can be generated using methods known inthe art and include those disclosed in WO2005118642, Ward et al., 1989,Nature, 341, 544-546 and Holt et al., 2003, Trends in Biotechnology, 21,484-490. In one embodiment a single domain antibody for use in presentinvention is a heavy chain variable domain (VH) or a light chain domain(VL). Each light chain domain may be either of the kappa or lambdasubgroup. Methods for isolating VH and VL domains have been described inthe art, see for example EP0368684 and Ward et al., supra. Such domainsmay be derived from any suitable species or antibody starting material.In one embodiment the single domain antibody may be derived from arodent, a human or other species. In one embodiment the single domainantibody is humanised.

In one embodiment the single domain antibody is derived from a phagedisplay library, using the methods described in for example,WO2005/118642, Jespers et al., 2004, Nature Biotechnology, 22, 1161-1165and Holt et al., 2003, Trends in Biotechnology, 21, 484-490. Preferablysuch single domain antibodies are fully human but may also be derivedfrom other species. It will be appreciated that the sequence of thesingle domain antibody once isolated may be modified to improve thecharacteristics of the single domain antibody, for example solubility,as described in Holt et al., supra.

In one embodiment the dAb is a human sequence obtained from scFvphage-display or from a transgenic Humouse™ or Velocimouse™ or ahumanised rodent.

In one embodiment, the dAb is obtained from a human or humanised rodent,a camelid or a shark. Such a dAb will preferably be humanised. In oneexample the single domain antibody is a VHH domain based on camelidimmunoglobulins as described in EP0656946. In one example, a camel or allama is immunised with an antigen of interest and blood collected whenthe titre is appropriate. The gene encoding the dAb may be cloned bysingle cell PCR, or the B cell(s) encoding the dAb may be immortalisedby EBV transformation, or by fusion to an immortal cell line.

As described herein above, the present invention provides dualspecificity antibody fusion proteins comprising an antibody Fab or Fab′fragment with specificity for an antigen of interest, said fragmentbeing fused to at least one single domain antibody, directly or via alinker, which has specificity for a second antigen of interest.

Accordingly, in one embodiment, the antibody fragment, eg. Fab or Fab′fragment is fused at the N-terminus of the heavy or the light chainvariable region to a dAb directly or via a linker. Alternatively, theantibody Fab or Fab′ fragment is fused at the C-terminus of the heavy orlight chain to a dAb directly or via a linker. In another embodiment theheavy and light chains of the antibody Fab or Fab′ fragment are eachfused at the C-terminus to a dAb directly or via a linker. The linkagecan be a chemical conjugation but is most preferably a translationfusion, i.e. a genetic fusion where the sequence of each is encoded insequence by an expression vector.

Typically the N-terminus of the single domain antibody will be fused tothe C-terminus of the heavy or light chain of the Fab or Fab′ fragment,directly or via a linker, and where the single domain antibody is fusedto the N-terminus of the Fab or Fab′ it will be fused via itsC-terminus, optionally via a linker.

In one embodiment the present invention provides a dual specificityantibody fusion protein comprising or consisting of an antibody Fab orFab′ fragment with specificity for an antigen of interest, said fragmentbeing fused to a single domain antibody at the N-terminus of the heavyor light chain which has specificity for a second antigen of interest.

In one embodiment the present invention provides a dual specificityantibody fusion protein comprising or consisting of an antibody Fab orFab′ fragment with specificity for an antigen of interest, said fragmentbeing fused to a single domain antibody at the C-terminus of the heavyor light chain which has specificity for a second antigen of interest.

In one embodiment the present invention provides a dual specificityantibody fusion protein comprising or consisting of an antibody Fab orFab′ fragment with specificity for an antigen of interest, said fragmentbeing fused to at least one single domain antibody at the C-terminus ofthe heavy or light chain which has specificity for a second antigen ofinterest.

In one embodiment the present invention provides a dual specificityantibody fusion protein comprising or consisting of an antibody Fab orFab′ fragment with specificity for an antigen of interest, said fragmentbeing fused to two single domain antibodies wherein each single domainantibody is fused in linear sequence to each other, optionally via alinker and the resulting single domain antibody fusion is fused to theC-terminus of the light chain or the heavy chain of the Fab or Fab′fragment.

In one embodiment the present invention provides a dual specificityantibody fusion protein comprising or consisting of an antibody Fab orFab′ fragment with specificity for an antigen of interest, said fragmentbeing fused to two single domain antibodies wherein one single domainantibody is fused to the C-terminus of the light chain of the Fab orFab′ fragment and the other single domain antibody is fused to theC-terminus of the heavy chain of the Fab or Fab′ fragment, said singledomain antibodies having specificity for a second antigen of interest.

In one embodiment where the heavy and light chains of the Fab or Fab′fragment each comprise a single domain antibody at the C-terminus thetwo single domain antibodies are identical i.e. have the same bindingspecificity for the same antigen. In one example, they bind the sameepitope on the same antigen. For example the single domain antibodiesmay both be the same VH dAb, the same VHH dAb or the same VL dAb.

Preferably where the heavy and light chains of the Fab or Fab′ fragmenteach comprise a single domain antibody at the C-terminus the two singledomain antibodies are a complementary VH/VL pair which bind the antigenco-operatively i.e. they are a complementary VH/VL pair which have thesame binding specificity. Typically they will be a VH/VL pair derivedfrom the same antibody.

In one embodiment, where the dual specificity antibody fusion protein ofthe present invention comprises two single domain antibodies which are acomplementary VH/VL pair, the VH single domain antibody is fused to theC-terminus of the heavy chain constant region (CH1) and the VL singledomain antibody is fused to the C-terminus of the light chain constantregion (C kappa or C lambda).

In one embodiment, where the dual specificity antibody fusion protein ofthe present invention comprises two single domain antibodies which are acomplementary VH/VL pair, the VL single domain antibody is fused to theC-terminus of the heavy chain constant region (CH1) and the VH singledomain antibody is fused to the C-terminus of the light chain constantregion (C kappa or C lambda).

In dual specificity fusion proteins of the present invention the singledomain antibody or antibodies bind to a second antigen, different fromthat bound by the Fab or Fab′ fragment component.

In one example the dAbs for use in the present invention exhibitspecificity for a complement pathway protein, a CD marker protein or anFcγR. In this case the dAb is preferably specific for a CD molecule.Most preferably, the dAb exhibits specificity for a CD molecule selectedfrom the group consisting of CD68, CD80, CD86, CD64, CD3, CD4, CD8 CD45,CD16 and CD35.

In a preferred example the dAbs for use in the present invention exhibitspecificity for a serum carrier protein, a circulating immunoglobulinmolecule, or CD35/CR1, the serum carrier protein preferably being ahuman serum carrier protein such as thyroxine-binding protein,transthyretin, α1-acid glycoprotein, transferrin, fibrinogen or serumalbumin. Most preferably, the dAb exhibits specificity for human serumalbumin. Thus, in one example, a rabbit, mouse, rat, camel or a llama isimmunised with a serum carrier protein, a circulating immunoglobulinmolecule, or CD35/CR1 (e.g. human serum albumin) and blood collectedwhen the titre is appropriate. The gene encoding the dAb may be clonedby single cell PCR, or the B cell(s) encoding the dAb may beimmortalised by EBV transformation, or by fusion to an immortal cellline. Alternatively the single domain antibody may be obtained by phagedisplay as described herein above.

In one embodiment the single domain antibody or antibodies bind humanserum albumin. In one embodiment the single domain antibody orantibodies bind human serum albumin, murine serum albumin and rat serumalbumin.

In one embodiment the single domain antibody which binds serum albuminis a dAb provided in WO2005/118642 (see for example FIGS. 1 c and 1d) ora VHH provided in WO2004/041862 or a humanised nanobody described in,for example table III of WO2006/122787.

In one embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a heavy chain VH singledomain antibody which comprises at least one of a CDR having thesequence given in FIG. 5 (e) SEQ ID NO:56 or FIG. 5 (k) SEQ ID NO:62 forCDR-H1, a CDR having the sequence given in FIG. 5( f) SEQ ID NO:57 orFIG. 5 (l) SEQ ID NO:63 for CDR-H2 and a CDR having the sequence givenin FIG. 5 (g) SEQ ID NO:58 or FIG. 5 (m) SEQ ID NO:64 for CDR-H3.

In another embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a heavy chain VH antibody,wherein at least two of CDR-H1, CDR-H2 and CDR-H3 of the VH domain areselected from the following: the sequence given in SEQ ID NO:56 or SEQID NO:62 for CDR-H1, the sequence given in SEQ ID NO:57 or SEQ ID NO:63for CDR-H2 and the sequence given in SEQ ID NO:58 or SEQ ID NO:64 forCDR-H3. For example, the single domain antibody may comprise a VH domainwherein CDR-H1 has the sequence given in SEQ ID NO:56 and CDR-H2 has thesequence given in SEQ ID NO:57. Alternatively, the single domainantibody may comprise a VH domain wherein CDR-H1 has the sequence givenin SEQ ID NO:56 and CDR-H3 has the sequence given in SEQ ID NO:58. Forthe avoidance of doubt, it is understood that all permutations areincluded.

In another embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a heavy chain VH singledomain antibody, wherein the VH domain comprises the sequence given inSEQ ID NO:56 for CDR-H1, the sequence given in SEQ ID NO:57 for CDR-H2and the sequence given in SEQ ID NO:58 for CDR-H3.

In another embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a heavy chain VH singledomain antibody, wherein the VH domain comprises the sequence given inSEQ ID NO:62 for CDR-H1, the sequence given in SEQ ID NO:63 for CDR-H2and the sequence given in SEQ ID NO:64 for CDR-H3.

In one embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a humanised heavy chain VHsingle domain antibody, dAbH1, having the sequence given in FIG. 5( a)(SEQ ID NO:52). An example of a suitable CH1-dAbH1 fusion comprising aG₄5 linker is given in FIG. 6 (SEQ ID NO:68).

In one embodiment the single domain antibody which binds human serumalbumin for use in the present invention is a humanised heavy chain VHsingle domain antibody, dAbH2, having the sequence given in FIG. 5( c)(SEQ ID NO:54). An example of a suitable CH1-dAbH2 fusion comprising aG₄5 linker is given in FIG. 6 (SEQ ID NO:69).

The residues in antibody variable domains are conventionally numberedaccording to a system devised by Kabat et al. This system is set forthin Kabat et al., 1987, in Sequences of Proteins of ImmunologicalInterest, US Department of Health and Human Services, NIH, USA(hereafter “Kabat et al. (supra)”). This numbering system is used in thepresent specification except where otherwise indicated.

The Kabat residue designations do not always correspond directly withthe linear numbering of the amino acid residues. The actual linear aminoacid sequence may contain fewer or additional amino acids than in thestrict Kabat numbering corresponding to a shortening of, or insertioninto, a structural component, whether framework or complementaritydetermining region (CDR), of the basic variable domain structure. Thecorrect Kabat numbering of residues may be determined for a givenantibody by alignment of residues of homology in the sequence of theantibody with a “standard” Kabat numbered sequence.

The CDRs of the heavy chain variable domain are located at residues31-35 (CDR-H1), residues 50-65 (CDR-H2) and residues 95-102 (CDR-H3)according to the Kabat numbering system. However, according to Chothia(Chothia, C. and Lesk, A. M. J. Mol. Biol., 196, 901-917 (1987)), theloop equivalent to CDR-H1 extends from residue 26 to residue 32. Thus‘CDR-H1’, as used herein, comprises residues 26 to 35, as described by acombination of the Kabat numbering system and Chothia's topological loopdefinition.

The CDRs of the light chain variable domain are located at residues24-34 (CDR-L1), residues 50-56 (CDR-L2) and residues 89-97 (CDR-L3)according to the Kabat numbering system.

In one embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a light chain VL singledomain antibody which comprises at least one of a CDR having thesequence given in FIG. 5( h) SEQ ID NO:59 or FIG. 5( n) SEQ ID NO:65 forCDR-L1, a CDR having the sequence given in FIG. 5( i) SEQ ID NO:60 orFIG. 5( o) SEQ ID NO:66 for CDR-L2 and a CDR having the sequence givenin FIG. 5( j) SEQ ID NO:61 or FIG. 5( p) SEQ ID NO:67 for CDR-L3.

In another embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a light chain VL antibody,wherein at least two of CDR-L1, CDR-L2 and CDR-L3 of the VL domain areselected from the following: the sequence given in SEQ ID NO:59 or SEQID NO:65 for CDR-L1, the sequence given in SEQ ID NO:60 or SEQ ID NO:66for CDR-L2 and the sequence given in SEQ ID NO:61 or SEQ ID NO:67 forCDR-L3. For example, the domain antibody may comprise a VL domainwherein CDR-L1 has the sequence given in SEQ ID NO:59 and CDR-L2 has thesequence given in SEQ ID NO:60. Alternatively, the domain antibody maycomprise a VL domain wherein CDR-L1 has the sequence given in SEQ IDNO:59 and CDR-L3 has the sequence given in SEQ ID NO:61. For theavoidance of doubt, it is understood that all permutations are included.

In another embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a light chain VL domainantibody, wherein the VL domain comprises the sequence given in SEQ IDNO:59 for CDR-L1, the sequence given in SEQ ID NO:60 for CDR-L2 and thesequence given in SEQ ID NO:61 for CDR-L3.

In another embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a light chain VL domainantibody, wherein the VL domain comprises the sequence given in SEQ IDNO:65 for CDR-L1, the sequence given in SEQ ID NO:66 for CDR-L2 and thesequence given in SEQ ID NO:67 for CDR-L3.

In one embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a humanised light chain VLsingle domain antibody, dAbL1, having the sequence given in FIG. 5( b)(SEQ ID NO:53). An example of a suitable CH1-dAbL1 fusion and aCkl-dAbL1 fusion both comprising a G₄5 linker is given in FIG. 6 (SEQ IDNO:70 and SEQ ID NO:72).

In one embodiment a single domain antibody which binds human serumalbumin for use in the present invention is a humanised light chain VLsingle domain antibody, dAbL2, having the sequence given in FIG. 5( d)(SEQ ID NO:55). An example of a suitable CH1-dAbL2 fusion and aCkl-dAbL2 fusion both comprising a G₄5 linker is given in FIG. 6 (SEQ IDNO:71 and SEQ ID NO:73).

In one embodiment where the heavy and light chains of the Fab or Fab′fragment each comprise a single domain antibody at the C-terminus andthe two single domain antibodies are a complementary VH/VL pair whichbind the antigen co-operatively as described herein above, the VH dAb isdAbH1 (SEQ ID NO:52) and the VL dAb is dAbL1 (SEQ ID NO:53).

In one embodiment where the heavy and light chains of the Fab or Fab′fragment each comprise a single domain antibody at the C-terminus thetwo single domain antibodies are a complementary VH/VL pair which bindthe antigen co-operatively as described herein above, the VH dAb isdAbH2 (SEQ ID NO:54) and the VL dAb is dAbL2 (SEQ ID NO:55).

In another aspect, the present invention provides albumin bindingantibodies or fragments thereof containing one or more of the CDRsprovided herein above and in FIG. 5( e-p). Said CDRs may be incorporatedinto any suitable antibody framework and into any suitable antibodyformat. Such antibodies include whole antibodies and functionally activefragments or derivatives thereof which may be, but are not limited to,monoclonal, humanised, fully human or chimeric antibodies. Accordingly,such albumin binding antibodies may comprise a complete antibodymolecule having full length heavy and light chains or a fragment thereofand may be, but are not limited to Fab, modified Fab, Fab′, F(ab′)₂, Fv,single domain antibodies, scFv, bi, tri or tetra-valent antibodies,Bis-scFv, diabodies, triabodies, tetrabodies and epitope-bindingfragments of any of the above (see for example Holliger and Hudson,2005, Nature Biotech. 23(9):1126-1136; Adair and Lawson, 2005, DrugDesign Reviews—Online 2(3), 209-217). The methods for creating andmanufacturing these antibody fragments are well known in the art (seefor example Verma et al., 1998, Journal of Immunological Methods, 216,165-181). Multi-valent antibodies may comprise multiple specificities ormay be monospecific (see for example WO 92/22853 and WO05/113605). Itwill be appreciated that this aspect of the invention also extends tovariants of these albumin binding antibodies.

It will be appreciated that such albumin binding antibodies, inparticular single domain antibodies may be conjugated to any otherantibody or protein or other molecule, as desired or used in any othersuitable context. In one example the single domain antibodies dAbH1,dAbL1, dAbH2, dAbL2 as described above and shown in FIG. 5( a-d) may beincorporated into any suitable antibody format or used as single domainantibodies in any suitable context, such as a fusion or conjugate.

In one embodiment antibodies of this aspect of the invention comprisethe sequence given in FIG. 5( e) for CDR-H1, the sequence given in FIG.5( f) for CDR-H2 and the sequence given in FIG. 5( g) for CDR-H3.

In one embodiment antibodies of this aspect of the invention comprisethe sequence given in FIG. 5( k) for CDR-H1, the sequence given in FIG.5( l) for CDR-H2 and the sequence given in FIG. 5( m) for CDR-H3.

In one embodiment antibodies of this aspect of the invention comprisethe sequence given in FIG. 5( h) for CDR-L1, the sequence given in FIG.5( i) for CDR-L2 and the sequence given in FIG. 5( j) for CDR-L3.

In one embodiment antibodies of this aspect of the invention comprisethe sequence given in FIG. 5( n) for CDR-L1, the sequence given in FIG.5( o) for CDR-L2 and the sequence given in FIG. 5( p) for CDR-L3.

Where the single domain antibody or antibodies of the dual specificityfusion protein of the present invention bind to albumin the bindingaffinity of the single domain antibody for albumin will be sufficient toextend the half-life of the Fab or Fab′ in vivo. It has been reportedthat an affinity for albumin of less than or equal to 2.5 μM affinitywill extend half-life in vivo (Nguyen, A. et al (2006) ProteinEngineering, Design & Selection, 19(7), 291-297). The single domainantibody molecules of the present invention preferably have a bindingaffinity suited to their purpose and the antigen to which they bind. Inone example the single domain antibodies have a high binding affinity,for example picomolar. In one example the single domain antibodies havea binding affinity for antigen which is nanomolar or micromolar.Affinity may be measured using any suitable method known in the art,including BIAcore as described in the Examples herein using natural orrecombinant antigen.

Preferably the single domain antibody molecules of the present inventionwhich bind albumin have a binding affinity of about 2 μM or better. Inone embodiment the single domain antibody molecule of the presentinvention has a binding affinity of about 1 μM or better. In oneembodiment the single domain antibody molecule of the present inventionhas a binding affinity of about 500 nM or better. In one embodiment thesingle domain antibody molecule of the present invention has a bindingaffinity of about 200 nM or better. In one embodiment the domainantibody molecule of the present invention has a binding affinity ofabout 1 nM or better. It will be appreciated that the affinity of singledomain antibodies provided by the present invention and known in the artmay be altered using any suitable method known in the art. The presentinvention therefore also relates to variants of the domain antibodymolecules of the present invention, which have an improved affinity foralbumin. Such variants can be obtained by a number of affinitymaturation protocols including mutating the CDRs (Yang et al., J. Mol.Biol., 254, 392-403, 1995), chain shuffling (Marks et al.,Bio/Technology, 10, 779-783, 1992), use of mutator strains of E. coli(Low et al., J. Mol. Biol., 250, 359-368, 1996), DNA shuffling (Pattenet al., Curr. Opin. Biotechnol., 8, 724-733, 1997), phage display(Thompson et al., J. Mol. Biol., 256, 77-88, 1996) and sexual PCR(Crameri et al., Nature, 391, 288-291, 1998). Vaughan et al. (supra)discusses these methods of affinity maturation.

The present invention also provides an isolated DNA sequence encoding adual specificity antibody fusion protein of the present invention. TheDNA sequences of the present invention may comprise synthetic DNA, forinstance produced by chemical processing, cDNA, genomic DNA or anycombination thereof.

DNA sequences which encode the dual specificity antibody fusion proteinof the present invention can be obtained by methods well known to thoseskilled in the art. For example, DNA sequences coding for part or all ofthe antibody fragments, linkers and/or dAbs may be synthesised asdesired from the determined DNA sequences or on the basis of thecorresponding amino acid sequences.

Standard techniques of molecular biology may be used to prepare DNAsequences coding for the dual specificity antibody fusion protein of thepresent invention. Desired DNA sequences may be synthesised completelyor in part using oligonucleotide synthesis techniques. Site-directedmutagenesis and polymerase chain reaction (PCR) techniques may be usedas appropriate.

The present invention further relates to a cloning or expression vectorcomprising one or more DNA sequences of the present invention.Accordingly, provided is a cloning or expression vector comprising oneor more DNA sequences encoding a dual specificity antibody fusionprotein of the present invention. In one preferred embodiment, thecloning or expression vector comprises a single DNA sequence encodingthe entire dual specificity antibody fusion protein. Thus, the cloningor expression vector comprises DNA encoded transcription units insequence such that a translation fusion protein is produced.

Indeed, it will be understood by those skilled in the art that a fusionprotein of the invention can have the dAb at the N-terminus or theC-terminus and thus, the dAb DNA encoded transcription unit will befirst or last, respectively, within the DNA sequence encoding thetranslation fusion. Thus, a translation fusion may comprise anN-terminal dAb and a C-terminal Fab or Fab′. Further, a translationfusion may comprise an N-terminal Fab or Fab′ and a C-terminal dAb.

It will be appreciated that the heavy chain and light chain of the Fabor Fab′ may be incorporated into the same or different vectors. In oneembodiment one vector may comprise a translation fusion comprising a Fabor Fab′ heavy chain and a C-terminal dAb and another vector may comprisea translation fusion comprising a Fab or Fab′ light chain and aC-terminal dAb.

For example, where the desire is to produce a dual specificity antibodyfusion protein with the dAb moiety at the N-terminal end of the antibodyfragment, the vector will comprise DNA transcription units in sequenceorder; a DNA transcription unit encoding the dAb moiety, optionally aDNA transcription unit encoding a linker sequence, and a DNAtranscription unit encoding an antibody fragment. Where the desire is toproduce a dual specificity antibody fusion protein with the dAb moietyat the C-terminal end of the antibody fragment, the vector will compriseDNA transcription units in sequence order; a DNA transcription unitencoding an antibody fragment, optionally a DNA transcription unitencoding a linker sequence, and a DNA transcription unit encoding dAbmoiety with specificity for a serum carrier protein, a circulatingimmunoglobulin molecule, or CD35/CR1, for example, human serum albumin.Thus, a translation fusion of the invention can be in differentconfigurations including, for example but without limitation,dAb-linker-Fab, Fab-linker-dAb, dAb-Fab, Fab-dAb, Fab′-dAb, dAb-Fab′,dAb-linker Fab′, Fab′-linker-dAb. Where two vectors are used forexample, the first may comprise the heavy chain of a Fab or Fab′ fusedto a dAb and the second may comprise the light chain of a Fab or Fab′fused to a dAb.

DNA code for an antibody fragment comprised within a translation fusionof the invention can be incorporated into a vector as a transcriptionunit in configurations as known to the person skilled in the art, forexample a transcription unit can comprise code for the light chainfollowed by the heavy chain code, or vice versa; see, in particular,Humphreys et al., 2002, Protein Expression and Purification, 26:309-320.

Preferably, a vector according to the present invention comprises anappropriate leader sequence, such as an antibody leader sequence. Suchleader sequences are well known in the art.

General methods by which the vectors may be constructed, transfectionand transformation methods and culture methods are well known to thoseskilled in the art. In this respect, reference is made to “CurrentProtocols in Molecular Biology”, 1999, F. M. Ausubel (ed), WileyInterscience, New York and the Maniatis Manual produced by Cold SpringHarbor Publishing.

Also provided is a host cell comprising one or more cloning orexpression vectors comprising one or more DNA sequences encoding a dualspecificity antibody fusion protein of the present invention. Anysuitable host cell/vector system may be used for expression of the DNAsequences encoding the dual specificity antibody fusion protein.Bacterial, for example E. coli, and other microbial systems may be usedor eukaryotic, for example mammalian, host cell expression systems mayalso be used. Suitable mammalian host cells include NS0, CHO, myeloma orhybridoma cells. Accordingly in one embodiment the fusion protein of thepresent invention is expressed in E. coli. In another embodiment thefusion protein of the present invention is expressed in mammalian cells.

The present invention also provides a process for the production of adual specificity antibody fusion protein comprising culturing a hostcell comprising a vector of the present invention under conditionssuitable for the expression of protein from the DNA sequence encodingsaid dual specificity antibody fusion protein. The invention furtherprovides methods for isolating the dual specificity antibody fusionprotein.

On production, a dual specificity antibody fusion protein of the presentinvention may be purified, where necessary, using any suitable methodknown in the art. For example, but without limitation, chromatographictechniques such as ion exchange, size exclusion, protein G orhydrophobic interaction chromatography may be used.

The size of a dual specificity antibody fusion protein may be confirmedby conventional methods known in the art such as size exclusionchromatography and non-reducing SDS-PAGE. Such techniques can be used toconfirm that the protein has not dimerised and/or does not have aportion missing, e.g. the dAb portion. If dimers are detected then themonomeric dual specificity antibody fusion protein may be purified awayfrom the dimeric species using conventional chromatography techniques asdescribed above.

Dual specificity antibody fusion proteins of the invention are useful inthe treatment of diseases or disorders including inflammatory diseasesand disorders, immune disease and disorders, fibrotic disorders andcancers.

The term “inflammatory disease” or “disorder” and “immune disease ordisorder” includes rheumatoid arthritis, psoriatic arthritis, still'sdisease, Muckle Wells disease, psoriasis, Crohn's disease, ulcerativecolitis, SLE (Systemic Lupus Erythematosus), asthma, allergic rhinitis,atopic dermatitis, multiple sclerosis, vasculitis, Type I diabetesmellitus, transplantation and graft-versus-host disease.

The term “fibrotic disorder” includes idiopathic pulmonary fibrosis(IPF), systemic sclerosis (or scleroderma), kidney fibrosis, diabeticnephropathy, IgA nephropathy, hypertension, end-stage renal disease,peritoneal fibrosis (continuous ambulatory peritoneal dialysis), livercirrhosis, age-related macular degeneration (ARMD), retinopathy, cardiacreactive fibrosis, scarring, keloids, burns, skin ulcers, angioplasty,coronary bypass surgery, arthroplasty and cataract surgery.

The term “cancer” includes a malignant new growth that arises fromepithelium, found in skin or, more commonly, the lining of body organs,for example: breast, ovary, prostate, lung, kidney, pancreas, stomach,bladder or bowel. Cancers tend to infiltrate into adjacent tissue andspread (metastasise) to distant organs, for example: to bone, liver,lung or the brain.

Thus, according to a further aspect of the invention, there is provideda pharmaceutical composition which comprises an antibody fusion of theinvention in association with one or more pharmaceutically acceptablecarriers, excipients or diluents. Also provided is the use of anantibody fusion protein of the invention for the manufacture of amedicament for the treatment of a disease or disorder. Most preferably,the disease or disorder is an inflammatory disease or disorder.

Pharmaceutical compositions according to the invention may take a formsuitable for oral, buccal, parenteral, subcutaneous, nasal, topical,ophthalmic or rectal administration, or a form suitable foradministration by inhalation or insufflation.

Where appropriate, for example if the single domain antibody orantibodies of the antibody fusion protein bind to albumin, it may bedesirable to pre-formulate the dual specificity fusion protein withhuman or recombinant serum albumin, using any suitable method known inthe art.

For oral administration, the pharmaceutical compositions may take theform of, for example, tablets, lozenges or capsules prepared byconventional means with pharmaceutically acceptable excipients such asbinding agents (e.g. pregelatinised maize starch, polyvinylpyrrolidoneor hydroxypropyl methyl cellulose); fillers (e.g. lactose,microcrystalline cellulose or calcium hydrogenphosphate); lubricants(e.g. magnesium stearate, talc or silica); disintegrants (e.g. potatostarch or sodium glycollate); or wetting agents (e.g. sodium laurylsulphate). The tablets may be coated by methods well known in the art.Liquid preparations for oral administration may take the form of, forexample, solutions, syrups or suspensions, or they may be presented as adry product for constitution with water or other suitable vehicle beforeuse. Such liquid preparations may be prepared by conventional means withpharmaceutically acceptable additives such as suspending agents,emulsifying agents, non-aqueous vehicles or preservatives. Thepreparations may also contain buffer salts, flavouring agents, colouringagents or sweetening agents, as appropriate.

Preparations for oral administration may be suitably formulated to givecontrolled release of the active compound.

For buccal administration, the compositions may take the form of tabletsor lozenges formulated in conventional manner.

The bispecific antibodies of the invention may be formulated forparenteral administration by injection, e.g. by bolus injection orinfusion. Formulations for injection may be presented in unit dosageform, e.g. in glass ampoules or multi-dose containers, e.g. glass vials.The compositions for injection may take such forms as suspensions,solutions or emulsions in oily or aqueous vehicles, and may containformulatory agents such as suspending, stabilising, preserving and/ordispersing agents. Alternatively, the active ingredient may be in powderform for constitution with a suitable vehicle, e.g. sterile pyrogen-freewater, before use.

In addition to the formulations described above, the bispecificantibodies of the invention may also be formulated as a depotpreparation. Such long-acting formulations may be administered byimplantation or by intramuscular injection.

For nasal administration or administration by inhalation, the compoundsaccording to the present invention may be conveniently delivered in theform of an aerosol spray presentation for pressurised packs or anebuliser, with the use of a suitable propellant, e.g.dichlorodifluoromethane, fluorotrichloromethane,dichlorotetrafluoroethane, carbon dioxide or other suitable gas ormixture of gases.

The compositions may, if desired, be presented in a pack or dispenserdevice which may contain one or more unit dosage forms containing theactive ingredient. The pack or dispensing device may be accompanied byinstructions for administration.

For topical administration the compounds according to the presentinvention may be conveniently formulated in a suitable ointmentcontaining the active component suspended or dissolved in one or morepharmaceutically acceptable carriers. Particular carriers include, forexample, mineral oil, liquid petroleum, propylene glycol,polyoxyethylene, polyoxypropylene, emulsifying wax and water.Alternatively, the compounds according to the present invention may beformulated in a suitable lotion containing the active componentsuspended or dissolved in one or more pharmaceutically acceptablecarriers. Particular carriers include, for example, mineral oil,sorbitan monostearate, polysorbate 60, cetyl esters wax, cetearylalcohol, benzyl alcohol, 2-octyldodecanol and water.

For ophthalmic administration the compounds according to the presentinvention may be conveniently formulated as microionized suspensions inisotonic, pH-adjusted sterile saline, either with or without apreservative such as a bactericidal or fungicidal agent, for examplephenylmercuric nitrate, benzylalkonium chloride or chlorhexidineacetate. Alternatively, for ophthalmic administration compounds may beformulated in an ointment such as petrolatum.

For rectal administration the compounds according to the presentinvention may be conveniently formulated as suppositories. These can beprepared by mixing the active component with a suitable non-irritatingexcipient which is solid at room temperature but liquid at rectaltemperature and so will melt in the rectum to release the activecomponent. Such materials include, for example, cocoa butter, beeswaxand polyethylene glycols.

The quantity of a compound of the invention required for the prophylaxisor treatment of a particular condition will vary depending on thecompound chosen and the condition of the patient to be treated. Ingeneral, however, daily dosages may range from around 10 ng/kg to 1000mg/kg, typically from 100 ng/kg to 100 mg/kg, e.g. around 0.01 mg/kg to40 mg/kg body weight for oral or buccal administration, from around 10ng/kg to 50 mg/kg body weight for parenteral administration, and fromaround 0.05 mg to around 1000 mg, e.g. from around 0.5 mg to around 1000mg, for nasal administration or administration by inhalation orinsufflation.

Preferred features of each embodiment of the invention are as for eachof the other embodiments mutatis mutandis. All publications, includingbut not limited to patents and patent applications cited in thisspecification are herein incorporated by reference as if each individualpublication were specifically and individually indicated to beincorporated by reference herein as though fully set forth.

The invention will now be described with reference to the followingexamples, which are merely illustrative and should not in any way beconstrued as limiting the scope of the present invention.

List of Figures:

FIG. 1: Diagrammatic representation of Fab-dAbs where the dAb is at theC-terminus

FIG. 2: Diagrammatic representation of Fab-didAbs

FIG. 3. SDS PAGE analysis of FabA-dAbL3 (CK-SG₄SE) (1) and FabA-dAbL3(CK-G[APAPA]₂) (2).

FIG. 4: Western blot analysis of FabA-dAbL3 (CK-SG₄SE) (1) andFabA-dAbL3 (CK-G[APAPA]₂) (2).

FIG. 4 a: SDS PAGE of FabB-didAbs

Lane M=SeeBlue markers

Lanes 1 & 2=IgG control

Lane 3=FabB

Lane 4=FabB-didAb, -dAbL1 (CK-G4Sx2) & dAbH1 (CH1-G4Sx2)

Lane 5=FabB-didAb, -dAbL2 (CK-G4Sx2) & dAbH2 (CHI-G4Sx2)

FIG. 5: Sequences of domain antibodies dAbH1 (a), dAbH2 (b), dAbL1 (c)and dAbL2 (d) and the CDRs derived from each of those antibodies. CDRsfor dAbH1 e) CDRH1:GIDLSNYAIN (SEQ ID NO:56); f) CDRH2:IIWASGTTFYATWAKG(SEQ ID NO:57); g) CDRH3:TVPGYSTAPYFDL (SEQ ID NO:58); CDRs for dAbH2 h)CDRL1:QSSPSVWSNFLS (SEQ ID NO:59); I) CDRL2:EASKLTS (SEQ ID NO:60); j)CDRL3:GGGYSSISDTT (SEQ ID NO:61); CDRs for dAbL1 k) CDRH1:GFSLSRYAMT(SEQ ID NO:62); l) CDRH2:TITTGGNTNYANWAKG (SEQ ID NO:63); m)CDRH3:GGYVSYADATELSL (SEQ ID NO:64); and CDRs for dAbL2 n)CDRL1:AQSQSIGSRLA (SEQ ID NO:65); o) CDRL2:YASTVAS (SEQ ID NO: 66); p)CDRL#:QSYDYSSSSSYA (SEQ ID NO:67).

FIG. 6: FabB-dAb constructs comprising FabB heavy or light chainvariable domain fused to a domain antibody. A—FabB-dabH1 (CH1-G₄Sx2);B—FabB-dabH2 (CH1-G₄Sx2); C—FabB-dabL1 (CH1-G₄Sx2); D—FabB-dabL2(CH1-G₄Sx2); E—FabB-dabL1 (CK-G₄Sx2); F—FabB-dabL2 (CK-G₄Sx2).

FIG. 7: Fab′A heavy and light chain sequences and FabA heavy chainsequence.

EXPERIMENTAL Example 1 Production of a dAb Specific for Human SerumAlbumin

An in-frame DNA encoded transcription unit encoding a dAb withspecificity for human serum albumin was produced using recombinant DNAtechnology.

Where desired an in-frame DNA encoded transcription unit encoding a dAbwith specificity for a recruitment protein can be produced usingrecombinant DNA technology.

Example 2 Production of Antibody Fragment

For fusion of a dAb to the C-terminus of the light chain, DNA wassynthesised encoding a human kappa light chain constant region (with theKm3 allotype of the kappa constant region), a peptide linker and a dAband cloned as a SacI-PvuII restriction fragment into the UCB-Celltechin-house expression vector pTTOD(Fab) (a derivative of pTTO-1, describedin Popplewell et al., Methods Mol. Biol. 2005; 308: 17-30) whichcontains DNA encoding the human gamma-1 CH1 constant region. This gaverise to a dicistronic gene arrangement consisting of the gene for thehumanised light chain fused via a linker to a dAb followed by the genefor the humanised heavy chain Fab fragment, both under the control ofthe tac promoter. Also encoded is a unique BspE1 site upstream of theGly4Ser linker, or an AscI site upstream of the Ala-Pro-rich linker.

For fusion of a dAb the C-terminus of the heavy chain, DNA wassynthesised encoding a human CH1 fragment (of the γ1 isotype) followedby a linker encoding sequence and a dAb. This was sublcloned as anApaI-EcoRI restriction fragment into the UCB-Celltech in-houseexpression vector pTTOD(Fab) (a derivative of pTTO-1, described inPopplewell et al., above) which contains DNA encoding the human gamma-1CH1 constant region. This gave rise to a dicistronic gene arrangementconsisting of the gene for the humanised light chain a non-codingintergenic sequence and followed by a heavy chain fused via a linker toa dAb, both under the control of the tac promoter. The recombinantexpression plasmid was transformed into the E. coli strain W3110 inwhich expression is induced by addition of IPTG. Expression experimentswere performed at small scale initially (5 ml culture volumes) withaddition of 200 uM IPTG at OD(600 nm) of approx. 0.5, cells wereharvested 2 hours post induction and extracted overnight at 30° C. inTris/EDTA. Clarified extracts were used for affinity analysis byBiacore. Constructs giving promising expression yields and activitieswere selected for fermentation.

Methods

In the following examples the antibody chain to which the dAb is fusedis denoted either as CK or LC for the cKappa light chain and as CH1 orHC for the heavy chain constant domain, CH1.

Construction of FabA-dAb Fusion Plasmids for Expression in E. coli

Fab-dAb fusion proteins were constructed by fusing dAbL3 or dAbH4 to theC-terminus of the constant region of either the light or heavy chain ofFabA. A flexible (SGGGGSE (SEQ ID NO:1)) or a rigid (G(APAPA)₂ (SEQ IDNO: 34)) linker was used to link the dAb to the cKappa region (SEQ IDNO:75) whereas the linker DKTHTS (SEQ ID NO:2) was used to link the dAbto the CHI region (SEQ ID

NO:76). The DNA sequence coding for the constant region-dAb fusion wasmanufactured synthetically as fragments to enable sub-cloning into theFabA sequence of the in-house pTTOD vector.

Light chain-dAb fusions were constructed by sub-cloning the SacI-ApaIfragment of the synthesized genes, encoding a C-terminal cKappa fused toeither dAbL3 or dAbH4 via either a (SGGGGSE (SEQ ID NO:1)) or a rigid(G(APAPA)₂ (SEQ ID NO: 34)) linker, into the corresponding sites of aplasmid capable of expressing FabA. Heavy chain-dAb fusions wereconstructed by sub-cloning the ApaI-EcoRI fragment of the synthesisedgenes, encoding a C-terminal CHI fused to either dAbL3 or dAbH4 via aDKTHTS linker, into the corresponding sites of a plasmid capable ofexpressing FabA.

Fab′ A is derived from an IL-1 beta binding antibody, the heavy andlight chain sequences of which are provided in SEQ ID NOs:74 and 75respectively as shown in FIG. 7. In Fab′A where the light chain has adAb attached, the hinge of the heavy chain was altered to DKTHTS evenwhere no dAb is attached to the heavy chain (SEQ ID NO:76).

FabA comprises the same light chain sequence (SEQ ID NO:75) and atruncated heavy chain sequence which terminates at the interchaincysteine (SEQ ID NO:77). dAbL3 and dAbH4 are light and heavy chaindomain antibodies respectively which bind human serum albumin.

Construction of FabA-didAb Fusion Plasmids for Expression in E. coli

FabA-didAb with dAbL3 or dAbH4 on both light and heavy chains wereconstructed by sub-cloning the ApaI-EcoRI fragment coding for CH1-dAbfusions into the existing Fab-dAb plasmids where the dAb is fused to thelight chain via the flexible linker.

Construction of FabB-dAb Fusion Plasmids for Expression in Mammaliancells The FabB-dAbs, FabB-dAbH1 (CH1-G₄Sx2), FabB-dAbH2 (CH1-G₄Sx2),FabB-dAbL1 (CH1-G₄Sx2), FabB-dAbL2 (CH1-G₄Sx2) were all assembled by PCRthen cloned into a mammalian expression vector under the control of theHCMV-MIE promoter and SV40E polyA sequence. These were paired with asimilar vector containing the FabB light chain for expression inmammalian cells (see below).

FabB is derived from an antibody which bids a cell surfaceco-stimulatory molecule. dAbH1, dAbH2, dAbL1 and dAbL2 were obtained asdescribed in Example 3.

Construction of FabB-dAb Fusion Plasmids for Expression in MammalianCells

The FabB-dAbs, FabB-dAbH1 (CH1-G₄Sx2), FabB-dAbH2 (CH1-G₄Sx2),FabB-dAbL1 (CK-G₄Sx2), FabB-dAbL2 (CK-G₄Sx2) were all assembled by PCRthen cloned into a mammalian expression vector under the control of theHCMV-MIE promoter and SV40E polyA sequence.

Mammalian Expression of FabB-dAbs and didAbs

HEK293 cells were transfected with the heavy and light chain plasmidsusing Invitrogen's 293fectin transfection reagent according to themanufacturer's instructions. Briefly, 2 μg heavy chain plasmid+2 μglight chain plasmid was incubated with 10 μl 293fectin+340 μl Optimemmedia for 20 mins at RT. The mixture was then added to 5×10⁶ HEK293cells in suspension and incubated for 4 days with shaking at 37° C.

Biacore

Binding affinities and kinetic parameters for the interactions ofFab-dAb constructs were determined by surface plasmon resonance (SPR)conducted on a Biacore T100 using CM5 sensor chips and HBS-EP (10 mMHEPES (pH7.4), 150 mM NaCl, 3 mM EDTA, 0.05% v/v surfactant P20) runningbuffer. Fab-dAb samples were captured to the sensor chip surface usingeither a human F(ab′)₂-specific goat Fab (Jackson ImmunoResearch,109-006-097) or an in-house generated anti human CH1 monoclonalantibody. Covalent immobilisation of the capture antibody was achievedby standard amine coupling chemistry.

Each assay cycle consisted of firstly capturing the Fab-dAb using a 1min injection, before an association phase consisting of a 3 mininjection of antigen, after which dissociation was monitored for 5 min.After each cycle, the capture surface was regenerated with 2×1 mininjections of 40 mM HCl followed by 30 s of 5 mM NaOH. The flow ratesused were 100 min for capture, 30 μl/min for association anddissociation phases, and 100 min for regeneration.

For kinetic assays, a titration of antigen (for human serum albumintypically 62.5 nM-2 μM, for IL-1β 1.25-40 nM) was performed, a blankflow-cell was used for reference subtraction and buffer-blank injectionswere included to subtract instrument noise and drift.

Kinetic parameters were determined by simultaneous global-fitting of theresulting sensorgrams to a standard 1:1 binding model using Biacore T100Evaluation software.

In order to test for simultaneous binding, 3 min injections of eitherseparate 5 μM HSA or 100 nM IL-1β, or a mixed solution of 5 μM HSA and100 nM IL-1β were injected over the captured Fab-dAb.

Fab-dAb Purification from E. coli

Periplasmic Extraction

E. coli pellets containing the Fab-dAbs within the periplasm werere-suspended in original culture volume with 100 mM Tris/HCl, 10 mM EDTApH 7.4. These suspensions were then incubated at 4° C. for 16 hours at250 rpm. The re-suspended pellets were centrifuged at 10000×g for 1 hourat 4° C. The supernatants were removed and 0.45 nm filtered.

Protein-G Capture

The Fab-dAbs were captured from the filtered supernatant by Protein-Gchromatography. Briefly the supernatants were applied, with a 20 minuteresidence time, to a Gammabind Plus Sepharose (GE Healthcare) columnequilibrated in 20 mM phosphate, 150 mM NaCl pH7.1. The column waswashed with 20 mM phosphate, 150 mM NaCl pH7.1 and the bound materialeluted with 0.1M glycine/HCl pH2.8. The elution peak was collected andpH adjusted to ˜pH5 with 1M sodium acetate. The pH adjusted elutionswere concentrated and diafiltered into 50 mM sodium acetate pH4.5 usinga 10 k MWCO membrane.

Ion Exchange

The Fab-dAbs were further purified by cation exchange chromatography atpH4.5 with a NaCl elution gradient. Briefly the diafiltered Protein-Geluates were applied to a Source15S (GE Healthcare) column equilibratedin 50 mM sodium acetate pH4.5. The column was washed with 50 mM sodiumacetate pH4.5 and the bound material eluted with a 20 column volumelinear gradient from 0 to 1M NaCl in 50 mM sodium acetate pH4.5. Thirdcolumn volume fractions were collected through out the gradient. Thefractions were analysed by A280 and SDS-PAGE and relevant fractionspooled.

Gel Filtration

If required the Fab-dAbs were further purified by gel filtration.Briefly the FabA-dAbL3 (CK-SG₄SE) pooled ion exchange elution fractionswere applied to a Superdex200 (GE Healthcare) column equilibrated in 50mM sodium acetate, 125 mM NaCl pH 5.0 and eluted with an isocraticgradient of 50 mM sodium acetate, 125 mM NaCl pH 5.0. 1/120 columnvolume fractions were collected through out the gradient. The fractionswere analysed by A280 and SDS-PAGE and relevant fractions pooled. ForFab-dAbs that did not undergo gel filtration, the pooled ion exchangeelution fractions were concentrated and diafiltered into 50 mM sodiumacetate, 125 mM NaCl pH 5.0 using a 10 k MWCO membrane.

SDS-PAGE

Samples were diluted with water where required and then to 10 μl wasadded 10 μL 2× sample running buffer. For non-reduced samples, 2 μL of100 mM NEM was added at this point, for reduced samples 2 μL of 10×reducing agent was added. The sample were vortexed, incubated at 85° C.for 5 mins, cooled and centrifuged at 12500 rpm for 30 secs. Theprepared samples were loaded on to a 4-20% acrylamine Tris/Glycine SDSgel and run for 100 mins at 125V. The gels were either transferred ontoPVDF membranes for Western blotting or stained with Coomassie Blueprotein stain.

Western Blotting

Gels were transferred to PVDF membranes in 12 mM Tris, 96 mM glycinepH8.3 for 16 hours at 150 mA. The PVDF membrane was block for 1 hr with2% Marvel™ in PBS+0.1% Tween20 (Blocking buffer)

Anti-Light Chain

HRP-rabbit anti-human kappa light chains, 1/5000 dilution in blockingbuffer for 1 hr.

Anti-Heavy Chain

mouse anti-human heavy chain, 1/7000 dilution in blocking buffer for 1hr. Followed by HRP-goat anti-mouse, 1/2000 dilution in blocking bufferfor 1 hr.

Anti-His Tag

rabbit anti-His6, 1/1000 dilution in blocking buffer for 1 hr. Followedby HRP-goat anti-rabbit IgG, 1/1000 dilution in blocking buffer for 1hr.

All blots were washed 6 times with 100 ml PBS+0.1% Tween20 for 10minutes per wash. The blots were developed with either ECL reagent for 1min before being exposed to Amersham Hyperfilm, or metal enhanced DABreagent for 20-30 minutes followed by water.

High Temperature Reverse Phase HPLC

Samples (2 μg) were analysed on a 2.1 mm C8 Poroshell column at 80° C.,with a flow rate of 2 ml/min and a gradient of 18-38% B over 4 mins.

A=0.1% TFA in H₂O

B=0.065% TFA in 80:20 IPA:MeOH

Detection is by absorption at 214 nm.

ELISA

The yields of Fab-dAb were measured using a sandwich ELISA. Briefly, theFab-dAb was captured with an anti-CH1 antibody then revealed with ananti-kappa-HRP.

Example 3

Generating Anti-Albumin Antibodies

½ lop rabbits were immunised with recombinant chromapure human serumalbumin (purchased from Jackson). Rabbits received 3 immunisations of100 ug HSA protein sub cutaneously, the first immunisation in completeFreunds adjuvant and subsequent immunisations in incomplete Freunds.Antibodies 1 and 2 which bind human, mouse and rat serum albumin wereisolated using the methods described in WO04/051268. Genes for the heavychain variable domain (VH) and light chain variable domain (VL) ofantibodies 1 and 2 were isolated and sequenced following cloning viareverse transcription PCR.

The light chain grafted sequences were sub-cloned into the rabbit lightchain expression vector pVRbcK which contains the DNA encoding therabbit C-Kappa constant region. The heavy chain grafted sequences weresub-cloned into the rabbit heavy chain expression vector pVRbHFab, whichcontains the DNA encoding the rabbit Fab′ heavy chain constant region.Plasmids were co-transfected into CHO cells and the antibodies producedscreened for albumin binding and affinity (Table 1). Transfections ofCHO cells were performed using the Lipofectamine™ 2000 procedureaccording to manufacturer's instructions (InVitrogen, catalogue No.11668).

Generating Humanised Domain Antibodies dAbL1, dAbH1, dAbL2 and dAbH2

Humanised VL and VH regions were designed using human V-region acceptorframeworks and donor residues in the framework regions. One grafted VLregion (L1 (SEQ ID NO:53) and L2 (SEQ ID NO:55)) and one VH region (H1(SEQ ID NO:52) and H2 (SEQ ID NO:54)) were designed for each ofantibodies 1 and 2 and genes were built by oligonucleotide assembly andPCR mutagenesis. The grafted domain antibodies and their CDRs are shownin FIG. 5.

TABLE 1 Affinities of anti-albumin antibodies as rabbit Fab as humanisedIgG Human SA murineSA Human SA nM nM nM Antibody 1 0.31 2.6 0.82Antibody 2 0.33 12 0.13

Example 4 Analysis of FabB-dAbs Expressed in Mammalian Cells

FabB-dAb constructs were produced as described in the methods and thesupernatants from the tranfected HEK293 cells containing the FabB-dAbswere tested directly in BIAcore.

Kinetic analysis was conducted to assess the interaction of HSA withFabB-dAb constructs. These consisted of either dAbL1, dAbH2 or dAbL3fused to the C-terminus of CH1 of FabB (See FIG. 6). The FabB-dAbL1 hasa higher affinity for HSA, K_(D)=170 nM, than FabB-dAbL3, K_(D)=392 nM.The FabB-dAbH2 was shown to possess the poorest affinity towards HSA,K_(D)=1074 nM, see Table 2.

TABLE 2 k_(a) k_(d) K_(D) Construct (×10⁴ M⁻¹s⁻¹) (×10⁻³ s⁻¹) (×10⁻⁹ M)FabB-dAbL1 (CH1-G₄Sx2) 1.91 ± 0.74 2.18 ± 1.21 170 ± 78 FabB-dAbH2(CH1-G₄Sx2) 2.66 ± 0.39  29 ± 4.76 1074 ± 42  FabB-dAbL3 (CH1-G₄Sx2)2.63 ± 0.39 9.87 ± 1.63  392 ± 119 Affinity and kinetic parametersdetermined for the binding of HSA to FabBs fused to dAbL1, dAbH2 ordAbL3. The data shown are mean values ± SEM. (For FabB-dAbL1 andFabB-dAbH2 n = 4. For FabB-dAbL3 n = 2).

SDS-PAGE and western blotting of the FabB-dAb proteins confirmed thatthe FabB-dAbs produced were of the expected size.

Example 5 Analysis of FabB-didAbs Expressed in Mammalian Cells

FabB-didAb constructs were produced as described in the methods and thesupernatants from the tranfected HEK293 cells containing the didAbstested directly in BIAcore.

Further analysis was performed using didAb constructs in which singledAbs were fused to both heavy and light C-termini of Fab. Constructs inwhich the didAb was derived from a natural heavy and light variabledomain pairing showed a marked improvement in affinity compared to thesingle dAb alone (table 2 and 3). The didAb fusion consisting of twoidentical dAbLls showed no improvement in affinity over that seen forthe single dAbL1 (data not shown).

TABLE 3 k_(a) k_(d) K_(D) Construct (×10⁴ M⁻¹s⁻¹) (×10⁻³ s⁻¹) (×10⁻⁹ M)FabB-didAb, -dAbL1 1.78 0.16 9 (CK-G₄Sx2) & dAbH1 (CH1-G₄Sx2)FabB-didAb, -dAbL2 0.54 0.21 39 (CK-G₄Sx2) & dAbH2 (CH1-G₄Sx2) Affinityand kinetic parameters determined for the binding of HSA to FabBs fusedto both dAbL1 & dAbH1 or dAbL2 & dAbH2.

SDS-PAGE of the FabB-didAb proteins confirmed that the FabB-didAbsexpressed well and were of the expected size (See FIG. 4 a). Note thisSDS PAGE gel is total protein expressed by the cell.

Example 6

Analysis of Purified FabA-dAbs

Plasmids for expression of the Fab-dAbs, Fab′A-dAbL3 (CK-SG₄SE)Fab′A-dAbL3 (CK-G[APAPA]₂) in E. coli were constructed as described inthe methods. The Fab-dAbs were expressed into the periplasm of the E.coli and purified to homogeneity as described in the methods. The purityof the Fab-dAbs were assessed by high temperature reverse phase HPLC,SDS-PAGE and Western blotting. The Fab-dAbs were also assessed forantigen binding by Biacore.

High Temperature Reverse Phase HPLC

High temperature reverse phase HPLC as performed as described in themethods gave quantitative analysis of all species contained inFabA-dAbL3 (CK-SG₄SE) and FabA-dAbL3 (CK-G[APAPA]₂). The percentage ofeach species present is shown in table 4.

TABLE 4 Quantification of species present in Fab-dAb batches Fab′A-dAbL3 Fab′ A-dAbL3 Species (CK-SG₄SE) (CK-G[APAPA]₂) 1 0.6% 1.8% 20.6% 0.0% 3 1.0% 0.3% 4 0.9% 0.8% Fab-dAb 85.5% 92.9% Di Fab-dAb 11.5%4.2%

SDS-PAGE

Fab-dAb samples were prepared under non-reduced and reduced conditionsand run on a gel as described in the methods. The gel was Coomassiestained. The banding profile of both Fab-dAb samples, Fab′A-dAbL3(CK-SG₄SE) and Fab′A-dAbL3 (CK-G[APAPA]₂), corresponds well to theprofile observed by high temperature reverse phase HPLC (FIG. 3).

Western Blot

Fab-dAb samples were subjected to non-reduced SDS-PAGE followed bywestern blot analysis with anti-light chain and anti-heavy chainantibodies as described in the methods. This confirmed that the dAb wason the light chain of the Fab and that the heavy chain was unmodified inboth samples (FIG. 4). It also demonstrates that all bands detected bycoomassie stained, non-reduced SDS PAGE are Fab-dAb related products.

Biacore

Kinetic analysis by SPR as described in the methods was used to assessthe binding of human serum albumin to Fab′A-dAbL3 (CK-SG₄SE) andFab′A-dAbL3 (CK-G[APAPA]₂). The results in table 5 demonstrate that bothconstructs are able to bind human serum albumin with a similar affinity(K_(D)) of approximately 1 μM.

TABLE 5 k_(a) k_(d) K_(D) Construct (×10⁴ M⁻¹s⁻¹) (×10⁻² s⁻¹) (×10⁻⁹ M)Fab′ A-dAbL3 3.44 1.42 411 (CK- SG₄SE) Fab′ A-dAbL3 9.61 2.85 296 (CK-G[APAPA]₂)

Further kinetic analysis demonstrated that all the fusion constructsretained the interaction characteristics of the original FabA towardsIL-1β, table 6, with only minor differences seen in the kinetic andaffinity parameters.

TABLE 6 k_(a) k_(d) K_(D) Construct (×10⁵ M⁻¹s⁻¹) (×10⁻⁵ s⁻¹) (×10⁻¹² M)Fab′ A-dAbL3 1.90 4.21 221 (CK- SG₄SE) Fab′ A-dAbL3 2.17 3.99 184 (CK-G[APAPA]₂) Fab′ A 2.02 6.46 320

The potential for each construct to bind simultaneously to both humanserum albumin and the IL-1β antigen was assessed by capturing eachconstruct to the sensor chip surface, before performing either separate3 min injections of 5 μM human serum albumin or 100 nM IL-1β, or a mixedsolution of both 5 μM human serum albumin and 100 nM IL-1μ. For eachFab-dAb construct the response seen for the combined HSA/IL-1β solutionwas almost identical to the sum of the responses of the independentinjections, see table 7. This shows that the Fab-dAbs are capable ofsimultaneous binding to both IL-1β and human serum albumin, and thatbinding of either IL-1β or human serum albumin does not inhibit theinteraction of the other. The original FabA bound only to IL-1β, withnegligible binding to human serum albumin.

TABLE 7 Construct Analyte Binding (RU) Fab′ A-dAbL3 (CK- SG₄SE) HSA +IL-1β 37.6 (37.9) HSA 13.2 IL-1β 24.7 Fab′ A-dAbL3 (CK- G[APAPA]₂) HSA +IL-1β 61.9 (63.6) HSA 30.7 IL-1β 32.9 Fab′ A HSA + IL-1β 30.3 (30.0) HSA1.3 IL-1β 28.7 The table above shows the binding response (RU) seen foreach construct after separate injections of HSA or IL-1β, or injectionof premixed HSA and IL-1β. In each case the final concentration was 5 μMfor HSA and 100 nM for IL-1β. The sum of the individual HSA and IL-1βresponses is shown in parentheses.

Example: 7 FabA didAbs

Expression of FabA-didAbs in E. coli

FabA-dAbs and FabA-didAb fusions terminating with a C-terminal HIS6 tagwere expressed in Escherichia coli. After periplasmic extraction, dAbfusion proteins were purified via the C-terminal His6 tag. Fabexpression was analysed by Western blotting of a non-reduced gel withanti-CH1 and anti-cKappa antibodies. FabA-dAb and FabA-didAb wereexpressed as full-length proteins and were shown to react to bothantibody detection reagents.

Analysis of FabA-didAbs Expressed in E. coli

Further analysis was conducted to characterise the binding of HSA toFabA constructs to which one or more dAbs were fused. Binding assayswere performed on a variety of constructs in which dAbL3 or dAbH4 fusedto either the light or heavy chain of the FabA (see Table 8 for detailsof the constructs and summary of the binding data). Although constructscarrying only dAbH4, on either the light or heavy chain, were seen tobind HSA with comparatively poor affinity (≈9 μM and 3 μM respectively),higher affinity binding was observed for constructs carrying dAbL3,either as a single fusion (on either light or heavy chain) or partneredwith a second dAb (dAbL3 or dAbH4) on the opposing chain.

TABLE 8 k_(a) k_(d) K_(D) Construct (×10⁴ M⁻¹s⁻¹) (×10⁻³ s⁻¹) (×10⁻⁹ M)FabA — — nb FabA-dAbL3 4.46 16.2 363 (LC-SG₄SE) FabA-dAbH4 — — 9142 (LCSG₄SE) FabA-dAbL3 8.24 15.4 187 (HC-DKTHTS) FabA-dAbH4 — — 2866(HC-DKTHTS) FabA-didAb, -dAbL3 3.00 15.1 502 (LC-SG₄SE) & -dAbL3(HC-DKTHTS) FabA-didAb, -dAbL3 4.36 16.3 373 (LC-SG₄SE) & -dAbH4(HC-DKTHTS) Affinity and kinetic parameters determined for the bindingof HSA to FabAs carrying dAbL3 or dAbH4 on either light chain (LC) orheavy chain (HC) or both as indicated. No binding (nb) of HSA to theoriginal FabA was detected. The interaction kinetics for the binding ofHSA to the FabA with (dAbH4 on HC) or (dAbH4 on LC), were too rapid todetermine, therefore affinity (K_(D)) was determined from steady-statebinding.

1. A dual specificity antibody fusion protein comprising an antibody Fabfragment or an antibody Fab′ fragment with specificity for an antigen ofinterest, said fragment being fused to two single domain antibodies thathave specificity for serum albumin, wherein one single domain antibodyis fused to the C-terminus of the light chain of the Fab fragment or theFab′ fragment and the other single domain antibody is fused to theC-terminus of the heavy chain of the Fab fragment or the Fab′ fragment,and wherein one single domain antibody is a VH domain comprising thesequence given in SEQ ID NO: 62 for CDR-H1, the sequence given in SEQ IDNO: 63 for CDR-H2 and the sequence given in SEQ ID NO: 64 for CDR-H3,and the other single domain antibody is a VL domain comprising thesequence given in SEQ ID NO: 65 for CDR-L1, the sequence given in SEQ IDNO: 66 for CDR-L2 and the sequence given in SEQ ID NO: 67 for CDR-L3,wherein the VH domain is fused to the C-terminus of the heavy chain ofthe Fab fragment or the Fab′ fragment and the VL domain is fused to theC-terminus of the light chain of the Fab fragment or the Fab′ fragment.2. The fusion protein according to claim 1 wherein each single domainantibody is humanised.
 3. The fusion protein according to claim 1wherein the Fab or Fab′ is humanised.
 4. The fusion protein according toclaim 1, wherein each single domain antibody fused to the antibody Fabor Fab′ fragment is fused via a linker of the amino acid sequencewherein the linker sequence is selected from the group consisting of SEQID NO: 1, SEQ ID NO: 2, SEQ ID NO: 3 and SEQ ID NO:
 45. 5. The fusionprotein according to claim 1, in which the VH domain is linked to theC-terminus of the heavy chain of the Fab or Fab′ fragment via a linkerhaving the sequence given in SEQ ID NO: 2 or SEQ ID NO: 45 and the VLdomain is linked to the C-terminus of the light chain of the Fab or Fab′fragment via a linker having the sequence given in SEQ ID NO: 1 or SEQID NO:
 45. 6. The fusion protein according to claim 1, wherein the serumalbumin is human serum albumin.
 7. A pharmaceutical compositioncomprising a dual specificity antibody fusion protein of claim 1.